All three admitted conspiring to produce class B drugs in what police described as a £2M a year operation.

They also illegally took £250,000 worth of electricity from a bypassed mains supply to power their illegal factory.

The inside of a cannabis factory in Chilmark, Wiltshire (Image: Wiltshire Police)

How were the men caught?

On February 22, 2017, officers carried out a midnight raid on RGHQ Chilmark in Wiltshire - an underground nuclear bunker built in the 1980s to keep local government officials safe in the event of a Cold War attack.

The site is no longer owned by the Ministry of Defence, however the bunker is still intact and the nuclear blast doors were still in place - making the site almost completely impenetrable.

Officers intercepted the three men as they left the bunker, having gathered intelligence on the site.

After detaining the men officers used keys found in their possession to gain entry to the bunker and found more than 4,000 cannabis plants inside - with the capability of producing £2M worth of drugs a year.

The inside of a cannabis factory in Chilmark, Wiltshire (Image: Wiltshire Police)

What do the police say about the crime?

Detective Inspector Simon Pope said: “This was an enormous discovery for our Local Priority Team – I believe it was the biggest cannabis factory we’ve ever had in Wiltshire and the South West region.

"The isolated and secure nature of the location made the warrant particularly challenging.

“The bunker itself had approximately 20 rooms inside over two floors, and almost every single room had been converted for the wholesale production of cannabis.

"In addition to the growing rooms, there were drying rooms, nurseries and living quarters for the growers – it was a sophisticated set up with an illegal connection to the mains electrical supply."

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He added: "I am delighted that the vast amount of preparation to ensure the warrant was executed successfully paid off, and that through the subsequent hard work of the team we were able to bring these three men to justice.

“I’m really pleased that we have been able to dismantle such a large-scale organised operation running in rural Wiltshire – as a result we have stopped an enormous amount of illegal drugs from reaching the streets of Wiltshire and the South West and causing harm to our communities.